Solid state diodes have been used as temperature sensors in the past. For example, transistors are used to sense temperatures in U.S. Pat. No. 4,071,813 and a thermal diode is described in U.S. Pat. No. 3,996,451.
More specifically, for temperature sensing, a field effect transistor is described in U.S. Pat. No. 3,801,949, a Schottsky barrier diode is used in U.S. Pat. No. 3,719,797, a silicon germanium sensor is described in U.S. Pat. No. 4,035,757, a monolithic semiconductor is used in U.S. Pat. No. 4,050,083, and an opposed pole Zener diode is described in U.S. Pat. No. 4,090,151.
All of the temperature sensors suffer from deficiencies of one kind or another when one attempts to utilize them over a wide temperature range, such as between 1.5.degree. K.-400.degree. K.
The most commonly commercially available solid state diode used for temperature sensing is one which includes gallium arsenide. Even when purchased in commercial quantities, these diodes cost as much as $100 each. But aside from cost, when used in a low temperature application, for example, on the order of 1.5.degree. K.-30.degree. K. where much cryogenic work is done, the response time for these diodes, and their sensitivity, due to their inherent method of construction, and because of their mass, is not as good as could be desired, and also when significant magnetic fields are impressed upon the low temperature environment being sensed (which is often the case in cryogenic research) many of the diodes mentioned above have problems with accuracy, and they also can be thrown out of calibration.